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Strain effects in correlated oxides from first principles

English title Strain effects in correlated oxides from first principles
Applicant Ederer Claude
Number 143265
Funding scheme Project funding (Div. I-III)
Research institution Departement Materialwissenschaft ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Condensed Matter Physics
Start/End 01.07.2013 - 30.06.2016
Approved amount 161'036.00
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All Disciplines (2)

Discipline
Condensed Matter Physics
Material Sciences

Keywords (5)

functional oxides; DFT+DMFT; thin films; strong correlations; epitaxial strain

Lay Summary (German)

Lead
Sogenannte "funktionale" Oxide haben eine grosse Anzahl von technologischen Anwendungsmöglichkeiten, z.B. in der Mikroelektronik. Dazu müssen die entsprechenden Materialien meist als dünne Filme auf einem geeigneten Substrat aufgewachsen werden. Die unterschiedlichen Kristallstrukturen führen dabei oft zu Verzerrungen, welche die Eigenschaften des Dünnschicht-Materials drastisch verändern können. Es ist daher sehr wichtig, die Auswirkungen solch "epitaktischer" Verzerrungen genau zu verstehen.
Lay summary

In diesem Projekt untersuchen wir den Effekt epitaktischer Verzerrungen auf die Eigenschaften "stark korrelierter" Oxide. Diese Materialien können z.B. unter dem Einfluss externer Stimuli (Temperaturänderungen, elektrische und/oder magnetische Felder) ihre Materialeigenschaften von elektrisch leitend zu isolierend (und umgekehrt) verändern. Dazu verwenden wir sogenannte "ab-initio" Rechnungen, die es uns ermöglichen, ausgehend von den atomaren quantenmechanischen Grundgleichungen, verschiedene Materialeigenschaften zu berechnen, und die zu erwartenden Veränderungen aufgrund epitaktischer Verzerrungen vorherzusagen.

Unsere Rechnungen ermöglichen es uns sowohl die physikalischen Mechanismen zu verstehen, welche die gewünschten Materialeigenschaften bestimmen, als auch optimale  Materialkombinationen und neuartige Effekte für zukünftige Anwendungen vorzuschlagen. Dies ist sehr wichtig im Hinblick auf die zukünftige Nutzung von funtionalen Oxiden in Energie-effizienteren und leistungsfähigeren mikro-elektronischen Bauteilen.

Direct link to Lay Summary Last update: 18.03.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Tuning the metal-insulator transition in d1 and d2 perovskites by epitaxial strain: A first-principles-based study
Sclauzero Gabriele, Dymkowski Krzysztof, Ederer Claude (2016), Tuning the metal-insulator transition in d1 and d2 perovskites by epitaxial strain: A first-principles-based study, in Physical Review B, 94, 245109.
Structural and electronic properties of epitaxially strained LaVO3 from density functional theory and dynamical mean-field theory
Sclauzero Gabriele, Ederer Claude (2015), Structural and electronic properties of epitaxially strained LaVO3 from density functional theory and dynamical mean-field theory, in Physical Review B, 92(23), 235112.
Strain-induced insulator-to-metal transition in LaTiO3 within DFT+DMFT
Dymkowski Krzysztof, Ederer Claude (2014), Strain-induced insulator-to-metal transition in LaTiO3 within DFT+DMFT, in Physical Review B, 89(16), 161109.

Collaboration

Group / person Country
Types of collaboration
Prof. Antoine Georges, University of Geneva Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Research Infrastructure
- Exchange of personnel
Dr. Thorsten Schmitt, Paul Scherrer Institute Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Prof. Silke Biermann, Ecole Polytechnique Paris France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Exchange of personnel
Prof. Philipp Werner, University of Fribourg Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Dr. Roman Kovacik, Forschungszentrum Julich Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Prof. Antoine Georges, Ecole Polytechnique Paris France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
CECAM Workshop "Computational methods towards engineering novel correlated materials" Talk given at a conference Tuning the metal-insulator transition in d1 and d2 perovskites by epitaxial strain 24.10.2016 Lausanne, Switzerland Ederer Claude;
International Summer School on Computational Quantum Materials Poster Breathing Mode Distortion and Magnetic Order in Rare-Earth Nickelates RNiO3 30.05.2016 Sherbrooke, Canada Hampel Alexander;
MRS Spring Meeting Talk given at a conference Strain-induced metal-insulator transitions in d2 and d2 perovskite transition metal oxides within DFT+DMFT 28.03.2016 Phoenix, AZ, United States of America Ederer Claude;
DPG Frühjahrstagung Talk given at a conference Breathing Mode Distortion and Magnetic Order in Rare-Earth Nickelates RNiO3 06.03.2016 Regensburg, Germany Hampel Alexander;
DPG Frühjahrstagung Talk given at a conference DFT+DMFT study of strain and interface effects in LaTiO3 and LaVO3 16.03.2015 Berlin, Germany Ederer Claude;
MRS Fall Meeting Talk given at a conference Strain-induced metal-insulator transitions in epitaxial films of perovskite titanates and vanadates by DFT+DMFT 01.12.2014 Boston, MA, United States of America Ederer Claude;
Strongly Correlated Electron Systems (SCES) 2014 Poster Strain-induced metal-insulator transitions in epitaxial films of perovskite titanates and vanadates by DFT+DMFT 07.07.2014 Grenoble, France Ederer Claude;
Annual Meeting of the Swiss Physical Society Poster Strain-induced metal-insulator transition in d1 perovskites within DFT+DMFT 30.06.2014 Fribourg, Switzerland Dymkowski Krzysztof;
APS March Meeting Talk given at a conference Strain-induced metal-insulator transitions in d1 perovskites within DFT+DMFT 03.03.2014 Denver, CO, United States of America Dymkowski Krzysztof;
Workshop on “Challenges in multiferroics/magnetoelectrics” Talk given at a conference Exploring strain effects in correlated oxides using the DFT+DMFT approach 04.12.2013 Strasbourg, France Ederer Claude;
Third Joint User’s Meeting at PSI Talk given at a conference Strain effects in correlated transition metal oxides from first principles 19.09.2013 Villingen, Switzerland Ederer Claude;


Abstract

In this project we will explore the effect of epitaxial strain on the fundamental properties of "correlated" transition metal (TM) oxides. In order to correctly describe both the effect of the specific crystal structure and chemistry of these materials as well as effects due to the electron-electron interaction, we will use a combination of first principles density functional theory (DFT) and dynamical mean-field theory (DMFT).In particular, we will focus on the prototypical systems with a d1 valence electron configuration: SrVO3 and LaTiO3. Both materials crystallize in the so-called perovskite crystal structure, but whereas SrVO3 is a rare example of an ideal perovskite, LaTiO3 exhibits slight deviations from the perfect perovskite structure, which manifest as a collective tilting of the oxygen network around the cartesian axes.It has recently been shown that the degree of this distortion determines whether the corresponding material is metallic or insulating. SrVO3 with its perfect 180 degrees V-O-V bonds is metallic, whereas in LaTiO3 the distortion of the bond angle away from the perfect 180 degrees creates a Mott insulator. On the other hand it has also been shown quite recently, that epitaxial strain, which is created in thin films by the lattice mismatch between the substrate and the thin film material, can significantly alter the nature of this octahedral tilt distortion. This poses the question of whether epitaxial strain can induce a metal-insulator transition or cause other interesting effects such as orbitally-selective Mott transitions, simply by altering the in-plane and out-of-plane TM-O-TM bond angles in different ways. Furthermore, the strain-induced changes in crystal-field, due to the tetragonally distorted unit cell, can also have pronounced effects on the electronic structure and it is currently unknown what is the resulting effect on the physical properties.These are the problems we will address in the proposed project. The clarification of these questions is important for various reasons. First, recent experiments have found metallic properties in thin film heterostructures of LaTiO3 and related materials. Such metallic properties can in principle be caused by the effects described above, but also through the presence of defects and inhomogeneities, or through the polar discontinuity at an oxide-oxide interface. Our calculations will be able to resolve this uncertainty. In addition, a good fundamental understanding of the effect of strain on the complex interplay between the various degreesof freedom in correlated electron systems is necessary to explore possible new phases and tailor the properties of these materials for future technological applications.Since conventional first principles methods such as e.g. the local-spin density approximation to DFT is fundamentally incapable of describing the Mott insulating state in LaTiO3 and similar compounds, a more advanced theoretical framework is required for a quantitative and predictive description of strain effects in these strongly correlated systems. Here we will use the combination of density functional theory and dynamical mean-field theory (DFT+DMFT) to address this problem. The DFT+DMFT approach has already successfully been applied to a variety of problems, in particular to explain why bulk LaTiO3 is a Mott-insulator whereas SrVO3 is acorrelated metal. However, at present the DFT+DMFT approach has not yet become a standard method for computational materials science. Our work will therefore also make an important contribution in establishing this approach as a practical tool for addressing a wider class of problems in materials science.
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